A4.1 演化與物種形成（生態系）：练习题

What is the fundamental requirement for the formation of a new species (speciation) from an existing population?

In some plant genera, such as Allium, speciation can occur rapidly through polyploidy. Which statement best explains this process?

In a population of flowering plants (\( 2n = 12 \)), a spontaneous doubling of chromosomes occurs during gamete formation, leading to the production of tetraploid individuals (\( 4n = 24 \)) within the same geographical area. These tetraploids are reproductively isolated from the original diploid population because their triploid hybrids (\( 3n \)) are sterile. Which statement best describes this phenomenon?

Which mechanism of reproductive isolation is occurring when two populations of a plant species flowering at different times of the year are unable to pollinate each other?

The accumulation of differences between groups which can lead to the formation of new species is known as:

Analyze how allopatric speciation leads to the formation of new species, detailing the role of geographical isolation and subsequent reproductive isolation.

Analyze how a population bottleneck can lead to rapid evolutionary changes and increase the likelihood of speciation within a surviving population.

Speciation can occur through various mechanisms that lead to reproductive isolation. In plants, a common mechanism is polyploidy. Consider two closely related plant species: Species A (\(2n = 14\)) and Species B (\(2n = 18\)).

(a) Describe the process of allopolyploidy that could lead to the formation of a new fertile species, Species C, from a hybrid of Species A and Species B. State the diploid chromosome number (\(2n\)) of Species C. (3 points)
(b) Explain why the initial hybrid produced by the mating of Species A and Species B is usually sterile, whereas Species C is fertile. (2 points)
(c) Identify the mode of speciation (allopatric or sympatric) represented by this event and explain how it results in immediate reproductive isolation. (2 points)

Speciation is the process by which new and distinct species are formed in the course of evolution.

(a) Compare and contrast allopatric and sympatric speciation, providing a specific mechanism or condition that can lead to reproductive isolation in each case.
(b) Discuss how hybrid zones can provide insight into the ongoing process of reproductive isolation and the potential outcomes of secondary contact between diverging populations.